A method for producing a surface-hardened material, comprising: an immersion step of immersing an iron steel material having nitrogen attached in the form of a solid solution on the surface thereof in a melt containing a chloride at a temperature ranging from 650° C. to 900° C.; and a cooling step of cooling the immersed iron steel material to a temperature equal to or lower than a martensitic transformation start temperature at a cooling rate equal to or higher than a lower critical cooling rare at which martensitic transformation starts.

A method for carburizing a steel member of the present invention includes: bringing a carburizing agent into contact with at least a part of a surface of a steel member; and heating the steel member and the carburizing agent to allow carbon to penetrate into at least a part of the surface, in which the carburizing agent contains a Fe-C alloy powder, a graphite powder in an amount of 20% by volume or more and 70% by volume or less relative to a total volume of the carburizing agent, and a binder that binds the Fe-C alloy powder and the graphite powder to each other, and in the heating, a heating temperature is held for a certain period of time within a temperature range of an austenite region of a eutectic point of the steel member or higher and lower than the peritectic point of the steel member.

A method for carburizing a steel member of the present invention includes: bringing a carburizing agent into contact with at least a part of a surface of a steel member; and heating the steel member and the carburizing agent to allow carbon to penetrate into at least a part of the surface, in which the carburizing agent contains a Fe-C alloy powder, a graphite powder in an amount of 20% by volume or more and 70% by volume or less relative to a total volume of the carburizing agent, and a binder that binds the Fe-C alloy powder and the graphite powder to each other, and in the heating, a heating temperature is held for a certain period of time within a temperature range of an austenite region of a eutectic point of the steel member or higher and lower than the peritectic point of the steel member.

Development of different inorganic materials, having the capacity to generate visible colors when excited in the infrared region, which can be used to determine the origin of explosives, fuses and ammunition, even after detonation, and in weapons and metal projectiles, thus serving as a safety marking tool thereof. The following were developed: LaNbO.sub.4 (called Mark1), BiVO.sub.4, Sr.sub.3V.sub.2O.sub.8 and YNbO.sub.4 (called Mark2), doped with different rare earth ions (erbium, ytterbium, holmium and thulium). The markers were physically inserted inside the explosives and in the gunpowder and by carburizing and forging in steel or metal alloy, with which the weapon or metal projectile is manufactured. The parameter used to demonstrate the presence of the markers in the products, after detonation or scraping of the weapon, was the verification of the color identity of the marker fluorescence, before and after, via laser in the infrared region.

Development of different inorganic materials, having the capacity to generate visible colors when excited in the infrared region, which can be used to determine the origin of explosives, fuses and ammunition, even after detonation, and in weapons and metal projectiles, thus serving as a safety marking tool thereof. The following were developed: LaNbO.sub.4 (called Mark1), BiVO.sub.4, Sr.sub.3V.sub.2O.sub.8 and YNbO.sub.4 (called Mark2), doped with different rare earth ions (erbium, ytterbium, holmium and thulium). The markers were physically inserted inside the explosives and in the gunpowder and by carburizing and forging in steel or metal alloy, with which the weapon or metal projectile is manufactured. The parameter used to demonstrate the presence of the markers in the products, after detonation or scraping of the weapon, was the verification of the color identity of the marker fluorescence, before and after, via laser in the infrared region.

Materials, methods and techniques relate to steel alloys. In some instances, steel alloys can include chromium, molybdenum, vanadium, copper, nickel, manganese, niobium, aluminum, and iron. In some instances, exemplary steel alloys are subjected to solution carburizing, tempering, and/or plasma nitriding. Exemplary steel alloys are typically precipitation strengthened carburizable and nitridable steel alloys.

A method of treating a surface of a gear for a strain wave reduction gear mechanism. The method includes: taking a gear for a strain wave reduction gear mechanism as a workpiece, the gear is formed from a machine structural steel containing at least 0.2% carbon and being subjected to heat treatment after having been machined; performing a first process in which carbide particles are ejected against a surface of the workpiece so as to remove machining marks on the surface of the workpiece and so as to cause elemental carbon in the carbide particles to diffuse and permeate into the surface of the gear; and after the first process, performing a second process in which spherical particles are ejected against a surface of the workpiece for increasing an internal compressive residual stress of the gear surface by a magnitude of at least −50 MPa.

A method of treating a surface of a gear for a strain wave reduction gear mechanism. The method includes: taking a gear for a strain wave reduction gear mechanism as a workpiece, the gear is formed from a machine structural steel containing at least 0.2% carbon and being subjected to heat treatment after having been machined; performing a first process in which carbide particles are ejected against a surface of the workpiece so as to remove machining marks on the surface of the workpiece and so as to cause elemental carbon in the carbide particles to diffuse and permeate into the surface of the gear; and after the first process, performing a second process in which spherical particles are ejected against a surface of the workpiece for increasing an internal compressive residual stress of the gear surface by a magnitude of at least −50 MPa.

A method of hardening a surface of a ferro-alloy object, the method comprising at least partially gasifying a carbon-containing polymer to form a hardening material source; and exposing the object to the hardening material source, such that the hardening material source and the surface of the object react, thereby hardening the surface of the object.

A method of hardening a surface of a ferro-alloy object, the method comprising at least partially gasifying a carbon-containing polymer to form a hardening material source; and exposing the object to the hardening material source, such that the hardening material source and the surface of the object react, thereby hardening the surface of the object.